This invention relates to a stage system for use in exposure apparatuses for a lithographic process in the manufacture of semiconductor devices, for example, or for use in various precision machining apparatuses or various precision measuring instruments, for example. In another aspect, the invention is concerned with an exposure apparatus with such a stage system and/or a device manufacturing method using the same.
As an exposure apparatus for the manufacture of semiconductor devices, for example, there is an apparatus called a stepper. In such a stepper, a pattern of an original such as a reticle or mask is printed repeatedly on a single substrate such as a wafer while moving stepwise the substrate relative to a projection optical system, for projecting the pattern to the substrate.
For a stage system for moving a wafer substrate stepwise relative to a projection optical system of a stepper and for positioning the substrate, a higher precision is required due to increasing density of integration of semiconductor devices.
On the other hand, recently, in order to increase the number of device products obtainable from a single wafer, that is, the productivity, the size of the wafer is increasing. This leads to enlargement in the size and weight of a stage system in a stepper. In order to assure a required precision under such a tendency, the dynamic characteristic of a stage system should be improved further. The rigidity of a guide should be enlarged, for example. However, this results in further enlargement in weight of the stage system as a whole.
In addition, for reduction of cost of a semiconductor device, it has been required to shorten the exposure cycle time to increase the throughput. Thus, high speed driving of a stage for moving a wafer, for example, is desired. However, in order to increase the speed of a large size and heavy weight stage, the rigidity of a supporting frame for supporting the stage must be enhanced. This results in considerable enlargement in size and weight of the whole mechanism as well as an increase of cost.
In X-ray exposure apparatuses which use recently developed soft X-rays (charged particle accumulation ring radiation light) as exposure light, a vertical type stage for holding a substrate such as a wafer in its upstanding position and for moving the substrate stepwise two-dimensionally along a vertical reference plane or a reference plane close to it, is used. In such a vertical type stage, in addition to the problems resulting from enlargement in size or increase of speed as described, there is another problem that: since the stage is to be moved in a gravity direction, use of a countermass mechanism, for example, is necessary for the weight compensation of the stage. However, any vibration of such a countermass mechanism will cause external disturbance that degrades wafer positioning precision. Thus, the dynamic characteristic of the stage is deteriorated remarkably.
FIGS. 27 and 28 show an example of such a vertical type stage. This stage comprises an X-Y stage including a Y stage 1120 which is reciprocally movable in a Y-axis direction (vertical direction) along a stage base 1110, mounted on a base 1110a, an X stage 1130 which is reciprocally movable in an X-axis direction along the Y stage 1120, a cylinder 140 for moving the Y stage 1120 in the Y-axis direction, and a linear motor (not shown) for moving the X stage 1130 in the X-axis direction.
The stage base 1110 has a guiding surface for supporting, without contact, the bottom face of the Y stage 1120 through air pads, for example. At an end of the stage base 1110, there is a Y guide (not shown) for guiding the Y stage 1120 in the Y-axis direction. The Y guide and the Y stage 1120 are kept out of contact with each other, by means of air pads, for example.
Weight compensation mechanism 1160 serves to cancel the weight of the Y stage 1120, the X stage 1130 and the wafer (not shown) held by it. The mechanism comprises a belt 1162 with the Y stage 1120 suspended at one end thereof and with a countermass 1161 suspended at another end thereof. The belt extends around and is supported by a pulley 1163. The weight of the countermass 1161 is set to be balanced with the weight of stage movable components, including the Y stage 1120, the X stage 1130 and the wafer held thereby.
With this arrangement, however, when the X stage moves in the X-axis direction upon the Y stage, the gravity center position of the stage movable components including the Y stage and X stage shifts. Thus, the balance of rotational moment about the Z axis (wZ-axis direction) changes. However, this moment can not be supported only by the countermass, and an excessively large load is applied to the Y guide (yaw guide) of the Y stage.
In order to support such a large load, the rigidity of the Y guide has to be enlarged. However, increasing the rigidity of the Y guide necessitates enlargement in size of the Y guide, for example. This results in further enlargement in size and weight of the stage mechanism as a whole, and causes degradation of the dynamic characteristic of the stage. Finally, improvement of positioning precision or positioning speed is disturbed.
For a belt that connects the stage and the countermass, generally, a steel belt or wire is used. When the stage moves, there occurs natural or proper vibration of several tens of Hz due to insufficiency of rigidity of the steel belt or the like. In addition to this, a natural vibration of not less than 50 Hz, for example, of the countermass itself is propagated through the belt to the stage. These vibrations degrade the stage positioning precision, and this is a large bar to improvement of the frequency response characteristic of the positioning control system.
It is an object of the present invention to provide an improved stage system by which a dynamic characteristic of a vertical type stage having a weight compensation mechanism such as a countermass can be improved, whereby enhancement of positioning speed and/or positioning precision can be accelerated considerably without enlargement in size of the mechanism.
It is another object of the present invention to provide an exposure apparatus and/or a device manufacturing method which uses such a stage system as described above.
In accordance with an aspect of the present invention, there is provided a stage system, comprising: a first stage movable along a reference plane, containing a vertical direction, and in the vertical direction or in a first direction close to the vertical direction; a second stage movable in a second direction intersecting with the first direction and relative to the first stage; a first driving mechanism for moving the first stage in the first direction; a second driving mechanism for moving the second stage in the second direction; a countermass movable in the first direction; and a third driving mechanism for moving the countermass in a direction opposite to the first direction.
In accordance with another aspect of the present invention, there is provided a stage system, comprising: a first stage movable along a reference plane, containing a vertical direction, and in the vertical direction or in a first direction close to the vertical direction; a second stage movable in a second direction intersecting with the first direction and relative to the first stage; a countermass movable in the first direction; a first driving mechanism for moving the first stage in the first direction; and a second driving mechanism for moving the second stage in the second direction; wherein said first driving mechanism includes a magnet and a coil one of which is mounted on one of the first stage and the countermass and the other of which is mounted on the other of the first stage and the countermass, such that the countermass moves in a direction opposite to the first stage.
In accordance with a further aspect of the present invention, there is provided a stage system, comprising: a stage movable along a reference plane, containing a vertical direction, and in the vertical direction or a direction close to the vertical direction; a countermass, balancing with a weight of the stage; connecting members for connecting the countermass to the stage; a pulley for supporting said connecting members; and an anti-vibration mechanism for reducing vibration to be propagated from said connecting members to the stage.
In accordance with a yet further aspect of the present invention, there is provided a stage system, comprising: a stage movable along a reference plane, containing a vertical direction, and in the vertical direction or a first direction close to the vertical direction; connecting members connected to the stage; a pulley for supporting said connecting members; a motor for rotationally driving the pulley and for compensating for a weight of the stage; and an anti-vibration mechanism for reducing vibration to be propagated from said connecting members to the stage.
In accordance with a still further aspect of the present invention, there is provided a stage system, comprising: a stage movable along a reference plane, containing a vertical direction, and in the vertical direction or a direction close to the vertical direction; a countermass, balancing with a weight of the stage; connecting members for connecting the countermass to the stage; a pulley for supporting said connecting members; and an actuator for adjusting one of a tension force of and an effective length of the connection members.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.